Composite sheet and cargo container comprising same

ABSTRACT

This invention is directed to a non-rigid composite sheet comprising in order (i) a first component having an areal density of from 88 to 678 gsm comprising a first fabric of filamentary yarns having a tenacity of at least 11 g/dtex and a UV and weather impervious first polymeric layer. (ii) a second component having an areal density of from 30 to 237 gsm comprising a flame resistant substrate and an inorganic refractory layer and (iii) a third component having an areal density of from 88 to 678 gsm comprising a second fabric of filamentary yarns having a tenacity of at least 11 g/dtex and an impact and scratch resistant second polymeric layer, the second fabric of the third component being adjacent to the refractory layer of the second component.

BACKGROUND

1. Field of the Invention

This invention pertains to a non-rigid composite sheet having fireresistant properties. The sheet is useful as walls in a cargo container,particularly containers used in aircraft.

2. Description of Related Art

Cargo containers or unitary load devices (ULDs) are used in aircraft,ships, road vehicles and railcars to carry goods. For economic reasonsthere is a desire to reduce the weight of an empty container whileminimizing its operational cost. Shipment of flammable materials in aircargo containers is creating a serious safety issue for airlines and aircargo carriers. There is increasing concern about the capability ofexisting containers to contain the spread of fire when the ignitionsource is the cargo itself. An example of such an ignition source is alithium-ion battery. Consequently, to prevent possible human casualtiesand cargo equipment losses, airlines and air cargo carriers are lookingfor flame resistant cargo containers to contain fires that may originatewithin the containers. A tightening of regulatory requirements isexpected over the next few years. There is therefore a need to provide alight weight cargo container having enhanced capability to contain thespread of fire from within the container that meet stringent durabilitystandards while providing an extended lifetime with minimum maintenance.

U.S. Pat. No. 8,292,027 to Richardson et al describes a compositelaminate comprising in order (a) a flame retardant polymeric moisturebarrier (b) an inorganic platelet layer and (c) a flame retardantthermoplastic film layer.

SUMMARY OF THE INVENTION

This invention is directed to a non-rigid composite sheet comprising inorder

-   -   (i) a first component having an areal density of from 88 to 678        gsm comprising a first fabric of filamentary yarns having a        tenacity of at least 11 g/dtex and a UV and weather impervious        first polymeric layer,    -   (ii) a second component having an areal density of from 30 to        237 gsm comprising a flame resistant substrate and an inorganic        refractory layer, and    -   (iii) a third component having an areal density of from 88 to        678 gsm comprising a second fabric of filamentary yarns having a        tenacity of at least 11 g/dtex and an impact and scratch        resistant second polymeric layer, the second fabric of the third        component being adjacent to the refractory layer of the second        component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show a perspective of a cargo container.

FIGS. 2A and 2D show a cross section through embodiments of a non-rigidcomposite sheet of this invention.

DETAILED DESCRIPTION

FIG. 1A shows at 10, a perspective of a fire resistant cargo containersuitable for aircraft, seagoing vessels and the like for containing theeffects of a fire within the cargo container comprising a frame assembly11, side walls 12 a, and 12 b and a top 13. FIG. 2B shows a containercomprising a frame assembly 11, a plurality of side walls 12 a to 12 d,a top 13 and a base 14. The side walls and ceiling comprise a non-rigidflame resistant composite sheet.

Non-Rigid Flame Resistant Composite Sheet.

FIG. 2A shows generally at 20 a cross section through the non-rigidflame resistant composite sheet which comprises in order a firstcomponent 21, a second component 22 and a third component 23. The sheetis arranged between the frames of a cargo container such that the thirdcomponent is the innermost component 31 facing towards the cargo and thefirst component is the outermost component 30 facing away from thecargo.

Preferably, the composite sheet has a break strength of at least 350N/cm (200 lb. per in.) when tested according to ASTM D3039/D3039M-08. Insome embodiments, the composite sheet has a break strength of at least525 N/cm (300 lb. per in.) or even of at least 700 N/cm (400 lb. perin.) Some embodiments of the composite sheet provides a penetrationresistance to a direct flame having a temperature of 927° C., +/−38° C.(1700° F., +/−100° F.) The specification also requires no flamepenetration of the specimen within five minutes after application of theflame source, and with the peak temperature measured at 101.6 mm (4inches) above the upper surface of the horizontal test sample notexceeding 204° C. (400° F.) when tested according to a flame penetrationFAA test method 14 CFR 25.855 Appendix F Part III—Test Method ToDetermine Flame Penetration Resistance of Cargo Compartment Liner(ceiling position).

Preferably, the composite sheet can withstand exposure to a temperaturerange of from −50° C. to +80° C. without compromising its reliabilityand durability over the life span of the end product.

In some embodiments, the first, second and third components mayoptionally be bonded to each other by means such as adhesives or thermallamination.

First Component

The first component 21 has an areal density of from 88 to 678 gsm (2.6to 20 oz. per sq. yd.) and comprises a first fabric 25 of filamentaryyarns having a tenacity of at least 11 grams per dtex (10 grams perdenier) and a first polymeric layer 24, the polymeric layer being theoutermost layer of the composite sheet. The polymeric layer provideschemical and environmental (i.e. weather and UV) resistance to bothphysical and chemical attack and permeation by liquids.

By chemical and environmental/weather resistant is meant that theability of the polymeric layer to withstand, without excessivedegradation, the effects of wind, rain, contaminants such as acidicand/or oily residues found in a typical industrial areas, and sunexposure. Preferably, the polymeric layer has an enhanced ability toresist damage by chemical reactivity, or solvent action, withhydrocarbons, chemicals, ozone, bacteria, fungus, and moisture, as wellas skin oils, typically associated with operation and maintenance of acommercial aircraft.

By UV resistant is meant that, when exposed to ultraviolet radiation,the polymeric layer retains its appearance and physical integritywithout an excessive degradation of its flexibility and mechanicalproperties (i.e. brittleness). Preferably, the polymeric layer blocks atleast 95% of UV rays, more preferably at least 98% and most preferably100% of UV rays. UV imperviousness of the first polymeric film can befurther mitigated by inclusion of additives in the polymeric material.Examples of such additives include fillers, colors, stabilizers andlubricants. The outer surface of the first polymeric layer that is notin contact with the first fabric may optionally be coated or treatedwith a UV blocking material.

Ultraviolet (UV) is an invisible band of radiation at the upper end ofthe visible light spectrum. At wavelengths ranging from 10 to 400 nm,ultraviolet (UV) starts at the end of visible light and ends at thebeginning of X-rays. As the primary exposure of the composite sheet toultraviolet light is the sun, the most critical UV resistance is that tothe lower-frequency, longer-wavelength rays.

Preferably, the outer polymeric layer has a soft, non-plastic feel thatis ideal for products that come in contact with the human skin andmaintains its toughness and flexibility over a wide temperature range,even at temperatures as low as −50° C. (−60° F.), over the life span ofthe product.

In some embodiments, the outer surface of the first polymeric layer,that is to say the surface not in contact with the first fabric, has arelease value of no more than 263 N/m (1.5 lb/in), more preferably nomore than 438 N/m (2.5 lb/in) when measured according to ASTM D2724-07(2011)e1 Standard Test Methods for Bonded, Fused, and Laminated ApparelFabrics. This facilitates cleaning, label removal etc.

In some embodiments, the first fabric layer may be bonded to the firstpolymeric layer by means such as an adhesive, thermal bonding or byfasteners.

In some embodiments, the bond strength between the first fabric and thefirst polymeric layer is at least 263 N/m (1.5 lb/in). In anotherembodiment, the bond strength between the first fabric and the firstpolymeric layer is at least 438 N/m (2.5 lb/in), or even at least 876N/m (5 lb/in).

The adhesive layer may be a thermoplastic or thermoset resin. Thermosetresins include epoxy, epoxy novolac, phenolic, polyurethane, andpolyimide. Thermoplastic resins include polyester, polyetherketone,polyetheretherketone, polyetherketoneketone, polyethersulfone, andpolyolefin. Thermoplastic resins are preferred.

Preferably, the adhesive layer may optionally contain up to 40 weightpercent of a flame retardant ingredient. Suitable flame retardantingredients include antimony trioxide, halogenated flame retardantsincluding tetrabromobisphenol A, polybrominated biphenyls,pentabrominateddiphenylether(oxide), octabrominateddiphenylether(oxide),decabrominateddiphenylyether(oxide) and hexabromocyclododecane.Phosphorus containing flame retardants are also widely used.

Preferably, the adhesive layer blocks at least 95% of UV rays, morepreferably at least 98% and most preferably 100% of UV rays. Theadhesive may further comprise fillers, colors, stabilizers, and otherperformance enhancing additives.

The adhesive must be capable of activation at a temperature in the rangeof 75 to 200 degrees C. In some embodiments, the activation range isfrom 120 to 140 degrees C. By activation we mean that for a thermosetresin, the resin must cure and bond to the polymeric layer and thefabric within the specified temperature range. For a thermoplasticresin, activation means that the resin softens and flows sufficiently tobond to the polymeric layer and the fabric. The adhesive bond betweenthe first polymeric layer and the first fabric is at least 263 N/m (1.5lb/in). In some embodiments, the adhesive bond between the firstpolymeric layer and the first fabric is at least 438 N/m (2.5 lb/in), oreven 876 N/m (5 lb/in).

Second Component

The second component has an areal density of from 30 to 237 gsm (0.9 to7 oz. per sq. yd.) and comprises a flame resistant substrate 26 and aninorganic refractory layer 27. In some embodiments, as shown in FIG. 2A,the substrate 26 of the second component is adjacent to the first fabric25 of the first component. In other embodiments, as shown in FIG. 2C,the substrate 26 of the second component is adjacent to the secondfabric 28 of the third component. Preferably, the substrate is a papercomprising from 40 to 70 weight percent of aramid fibers and from 30 to60 weight percent of polymeric binder. The paper

(i) has a dry tensile strength of at least 1225 N/m (7 lb/in) in a firstdirection and at least 525 N/m (3 lb/in) in a second direction, thesecond direction being transverse to the first direction,

(ii) has a thickness of from 0.025 to 0.175 mm, and

(iii) has a basis weight of from 20 to 70 gsm.

In one embodiment, a paper substrate comprises from 40 to 70 weightpercent of aramid fibers and from 30 to 60 weight percent of binder. Inanother embodiment, the substrate comprises from 40 to 55 weight percentof aramid fibers and from 45 to 60 weight percent of binder. In someother embodiment, the substrate comprises from 40 to 90 weight percentof aramid fibers and from 10 to 60 weight percent of binder. In yetanother embodiment, the substrate comprises from 40 to 60 weight percentof aramid fibers and from 40 to 60 weight percent of binder. A preferredbinder is meta-aramid.

The thickness of a paper substrate used in this invention is dependentupon the end use or desired properties of the laminate but, to providean overall high flexibility and the lowest possible weight, is typicallyfrom 1 to 7 mils (0.025 to 0.175 mm) or even from 3 to 7 mils (0.075 to0.175 mm) thick. The substrate thickness may even be from 4 to 6 mils(0.100 to 0.150 mm). A substrate thickness below 1 mil would result inundesirable features such as a weaker and less dimensionally stablesecond component, especially when saturated with water. A substratehaving a thickness greater than 7 mils would add undesirable weight andstiffness.

In some embodiments, the basis weight of a paper substrate is from 17 to170 gsm (0.5 to 5.0 oz. per sq. yd.) or from 27 to 47 gsm (0.8 to 1.4oz. per sq. yd.).

A paper substrate has a dry tensile strength of at least 7 lb/in in afirst direction and at least 3 lb/in in a second direction, the seconddirection being transverse to the first direction. By dry tensilestrength we mean the tensile strength of a paper that has beenconditioned at ambient temperature and humidity, typically 48-52%Relative Humidity and 22-24 degrees C. TAPPI T-402 sp-08 is an examplespecification defining ambient conditions for paper, board and pulpproducts. A dry tensile strength of at least 7 lb/in in a firstdirection is required to ensure proper handling of the coated webthrough the subsequent process steps, in particular, to ensure tightroll formation during winding to prevent roll sagging and telescoping.

In some embodiments, a paper substrate has a dry tensile strength of atleast 10 lb/in in the first direction and at least 5 lb/in in the seconddirection.

To aid manufacture of the second component, it is preferable that

(i) the paper substrate is hydrophilic. This feature aids the dryingprocess. As the majority of the water from the refractory coatingdispersion is absorbed by the substrate, this allows more efficientdrying and forming of the inorganic refractory layer as well aspreventing drying defects such as blisters in the refractory layer.

(ii) the paper substrate has an air permeability no greater than 600Gurley Air Resistance (sec/100 cc, 20 oz. cyl). An air permeability ofgreater than 600 Gurley Air Resistance would adversely affect the dryingprocess of the coated paper. In some embodiments, the paper has an airpermeability of from 250 to 350 Gurley Air Resistance (sec/100 cc, 20oz. cyl.).

(iii) the paper substrate has a wet tensile strength of at least 525 N/m(3 lb/in) in a first direction and at least 350 N/m (2 lb/in) in asecond direction, the second direction being transverse to the firstdirection. In another embodiment, the paper has a wet tensile strengthof at least 875 N/m (5 lb/in) in a first direction and at least 350 N/m(2 lb/in) in a second direction, the second direction being transverseto the first direction. In a preferred embodiment the first direction isthe long direction within the plane of the paper, that is, the directionin which the roll of paper has been made. This is also known as themachine direction. The second direction is sometimes known as the crossdirection. By wet tensile strength we mean the tensile strength of thepaper after saturation with water. If the wet tensile strength is lessthan 525 N/m (3 lb/in) in a first direction, there is a high risk offrequent sheet breaks during the coating process due to the weight beingdeposited on the paper and the tension applied to the paper,

(iv) the paper substrate has a surface smoothness on the surface that isin contact with the refractory layer of no less than 250 Sheffieldunits, Smoothness is concerned with the surface contour of paper. It isthe flatness of the surface under testing conditions which considersroughness, levelness, and compressibility. This test is an indirectmeasure of paper smoothness or roughness. The Sheffield test method is ameasurement of air flow between the test specimen (backed by flat glasson the bottom side) and two pressurized, concentric annular lands thatare impressed in to the sample from top. Such a procedure is describedin TAPPI T-538 om-08. In some embodiments, the substrate has a surfacesmoothness on at least one surface of from 300 to 400 Sheffield units,and

(v) the paper substrate has a density of from 0.25 to 0.6 g/cc or from0.25 to 0.45 g/cc or even from 0.30 to 0.40 g/cc. A substrate density ofbelow 0.25 g/cc would result in undesirable features such as a weakerfluffy and excessively open structure. For papers with over 30 weightpercent of polymeric binder, a substrate density of greater than 0.6g/cc would require an excessive densification that would alter bothsurface properties (i.e. higher smoothness) and air permeability of thedensified paper. Increased surface smoothness of the densified substratewould result in a lower release value potentially leading to inorganicrefractory layer peeling off the densified substrate with a risk ofbreaks in the refractory layer. Lower air permeability would hinder thedrying process of the coated paper.

The aramid fibers of the paper may be meta-aramid, para-aramid or acombination of the two.

The high temperature properties of the aramid fibers ensure thermal andmechanical stability of the paper substrate during processing steps whenthe substrate can be exposed to a temperature of 150 degrees C. for atleast 10 minutes, that is to say, that the paper will not changedimensions when subjected to a temperature of 150 degrees C. for atleast 10 minutes.

The aramid fibers of the paper can be in the form of floc, pulp, or acombination of thereof. As employed herein the term aramid means apolyamide wherein at least 85% of the amide (—CONH—) linkages areattached directly to two aromatic rings. Additives can be used with thearamid. In fact, it has been found that up to as much as 10 percent, byweight, of other polymeric material can be blended with the aramid orthat copolymers can be used having as much as 10 percent of otherdiamine substituted for the diamine of the aramid or as much as 10percent of other diacid chloride substituted for the diacid chloride ofthe aramid.

Floc is generally made by cutting continuous spun filaments intospecific-length pieces. If the floc length is less than 2 millimeters,it is generally too short to provide a paper with adequate strength; ifthe floc length is more than 25 millimeters, it is very difficult toform uniform wet-laid webs. Floc having a diameter of less than 5micrometers, and especially less than 3 micrometers, is difficult toproduce with adequate cross sectional uniformity and reproducibility; ifthe floc diameter is more than 20 micrometers, it is very difficult toform uniform papers of light to medium basis weights.

The term “pulp”, as used herein, means particles of fibrous materialhaving a stalk and fibrils extending generally therefrom, wherein thestalk is generally columnar and 10 to 50 micrometers in diameter and thefibrils are fine, hair-like members generally attached to the stalkmeasuring only a fraction of a micrometer or a few micrometers indiameter and 10 to 100 micrometers long. Aramid fiber floc is of asimilar length to carbon fiber floc. Both meta and para aramid fibersare suitable and are available from E.I. DuPont de Nemours, Wilmington,Del. (DuPont) under the tradenames Kevlar® and Nomex® and from TeijinTwaron, Conyers, Ga. under the tradename Twaron®.

A preferred pulp material is p-aramid. However a blend of p-aramid withother synthetic or natural fibers such as liquid crystal polyester,polyareneazole, meta-aramid, and cellulose can be utilized. Oneillustrative process for making aramid pulp is disclosed in U.S. Pat.No. 5,084,136 to Haines et al.

Different thermoset and thermoplastic resins can be used as a polymericbinder in the paper of this invention. These resins can be supplied inthe form of fibrids, flakes, powder, and floc. The term “fibrids” asused herein, means a very finely-divided polymer product of small,filmy, essentially two-dimensional, particles known having a length andwidth of 100 to 1000 micrometers and a thickness of 0.1 to 1 micrometer.Preferable types of binder resins are aramids, polyimides, phenolics,and epoxies. However, other types of the resins can also be used.

Fibrids are typically made by streaming a polymer solution into acoagulating bath of liquid that is immiscible with the solvent of thesolution. The stream of polymer solution is subjected to strenuousshearing forces and turbulence as the polymer is coagulated. The fibridmaterial of this invention can be selected from meta or para-aramid orblends thereof. More preferably, the fibrid is a meta-aramid.

The paper can include inorganic particles such as mica, vermiculite,ceramic fiber and blends thereof. Alumina-silicate fiber is an exampleof a ceramic fiber. For example, Nomex® 418 and Nomex® 419 are papersavailable from DuPont comprising a blend of m-aramid fibers and mica,the mica being present in an amount of about 50 weight percent. Theaddition of these performance enhancing additives is to impartproperties such as improved fire resistance, thermal conductivity,dimensional stability, and the like to the paper and the compositesheet.

Exemplary combinations of fibrids and floc include m-aramid fibrids andm-aramid floc; m-aramid fibrids and p-aramid floc; m-aramid fibrids anda blend of p-aramid floc and polethyleneterephthalate (PET) floc;p-aramid fibrids and p-aramid floc; and p-aramid fibrids with p-aramidpulp and p-aramid floc.

In one preferred embodiment, the fiber and the polymer binder in theform of fibrids can be slurried together to form a mix that is convertedto paper on a wire screen or belt. Reference is made to U.S. Pat. Nos.4,698,267 and 4,729,921 to Tokarsky; U.S. Pat. No. 5,026,456 to Hesleret al.; U.S. Pat. Nos. 5,223,094 and 5,314,742 to Kirayoglu et al forillustrative processes for forming papers from aramid fibers and aramidfibrids.

Once the paper is formed, it may be calendered to the desired voidcontent/apparent density.

Another form of substrate includes a nonwoven fibrous sheet comprisingfibers wherein the fibers are glass, aramid, crystalline ceramic oxide(including quartz), silicon nitride, silicon carbide, oxidizedpolyacrylonitrile, carbon, and combinations thereof.

In some embodiments, as shown in FIGS. 2B and 2D, the second componentmay include a protective polymeric layer 32 in contact with therefractory layer 27. Such a protective polymeric layer providesmechanical reinforcement and protection to the refractory layer duringmanufacturing, installation and service. In a preferred embodiment, theprotective polymeric layer is in a form of a self-supporting film.

In some embodiments, the protective polymeric layer 32 may be bonded tothe refractory layer 27 by means such as an adhesive or thermal bonding.In some embodiments, the bond strength between the protective polymericlayer and the refractory layer is at least 44 N/m (0.25 lb/in). Inanother embodiment, the bond strength between the protective polymericlayer and the refractory layer is at least 140 N/m (0.8 lb/in) or evenat least 262 N/m (1.5 lb/in.).

The protective polymeric layer 32 must be capable of withstanding atemperature of at least 200 degrees C. for at least 10 min. Thepolymeric layer may be a thermoset or thermoplastic material. Athermoplastic layer is preferred.

Preferably the protective layer 32 should have a UL 94 flameclassification of V-0. UL 94 flame classification is an UnderwritersLaboratory test, The Standard for Flammability of Plastic Materials forParts in Devices and Appliances, which measures a material's tendencyeither to extinguish or to spread the flame once the specimen has beenignited. V-0 indicates that the material is tested in a verticalposition and self-extinguished within ten seconds after the ignitionsource is removed.

Preferably, the protective layer has a thickness in the range of from 4to 30 micrometers. More preferably the thickness range should be from 5to 15 micrometers and most preferably in the range from 5 to 7micrometers. The layer further provides mechanical strength andstiffness to the laminate.

Suitable materials for the protective layer include polyketone,polyimide, polysulfone, polyarylene sulfide, fluoropolymers, liquidcrystal polymers and polycarbonate. Examples of polyketone arepolyetheretherketone (PEEK) and polyetherketoneketone (PEKK).Polyethersulfone and polyphenylsulfone are examples of polysulfone.Poly(p-phenylene sulfide is a suitable polyarylene sulfide for use inthis invention. Polyvinylfluoride (PVF) and polyvinylidinefluoride(PVDF) are examples of fluoropolymers. A suitable fluoropolymer isavailable from DuPont under the tradename Tedlar. Polyarylate is anexample of a suitable liquid crystal polymer. Some of these films mayalso be coated with a second polymeric material. For example, apolyimide film, Kapton®, may be coated with fluorinated ethylenepropylene, FEP and used in this invention.

The surface of the protective layer 32 may optionally be treated toimprove adhesion with another substrate such as an adhesive. Suitablesurface treatment methods include, but are not limited to, coronaetching and washing with coupling agents such as ammonium, phosphoniumor sulfonium salts. Where the protective layer is adhesively bonded tothe refractory layer 27 and the fabric layer 28, the adhesive may be athermoplastic or thermoset resin. Thermoset resins include epoxy, epoxynovolac, phenolic, polyurethane, and polyimide. Thermoplastic resinsinclude polyester, polyetherketone, polyetheretherketone,polyetherketoneketone, polyethersulfone, and polyolefin. Thermoplasticresins are preferred.

To prevent possible damage from mechanical stressing exerted by ashrinking or melting or disintegrating protective polymeric layer on theinorganic refractory layer during a flame propagating event, it ispreferred that inter-ply bond of the composite laminate would fail (i.e.release or melt or soften) in the early stage of the flame exposure thuscausing internal debonding of the composite laminate. That is to say,delamination of the refractory layer from the protective film will occurbefore the protective film starts disintegrating. Due to theirrelatively low activation temperatures, thermoplastic adhesives are apreferred choice over thermoset adhesives as they will facilitateeffective delamination.

The adhesive layer used to bond the protective layer to the refractorylayer may optionally contain up to 40 weight percent of a flameretardant ingredient. Suitable flame retardant ingredients includeantimony trioxide, halogenated flame retardants includingtetrabromobisphenol A, polybrominated biphenyls,pentabrominateddiphenylether(oxide), octabrominateddiphenylether(oxide),decabrominateddiphenylyether(oxide) and hexabromocyclododecane.Phosphorus containing flame retardants are also widely used.

Preferably, the adhesive should be capable of activation at atemperature in the range of 75 to 200 degrees C. In some embodiments,the activation range is from 120 to 140 degrees C. By activation we meanthat for a thermoset resin, the resin must bond to the polymeric layerand the fabric within the specified temperature range. For athermoplastic resin, activation means that the resin softens and flowssufficiently to bond to the polymeric layer and the fabric.

Inorganic Refractory Layer

The inorganic refractory layer, shown as 12 in FIG. 1, is adjacent to atleast one surface of the substrate. Preferably, the refractory layer hasa dry areal weight of from 15 to 50 gsm or even from 20 to 35 gsm.Preferably the refractory layer has a residual moisture content of nogreater than 10 percent by weight, more preferably no greater than 3percent by weight.

The refractory layer comprises platelets. Preferably at least 85% of thelayer comprises platelets, more preferably at least 90% and mostpreferably at least 95%. In some embodiments, platelets comprise 100% ofthe layer. The refractory layer may comprise some residual dispersantarising from incomplete drying of the platelet dispersion duringmanufacture.

The refractory layer has a thickness of from 7.0 to 76 micrometers andmore preferably from 7.0 to 50 micrometers. Preferably, the layer has aUL 94 flame classification of V-0. The function of the refractory layer,in which adjacent platelets overlap, is to provide a flame and hot gasimpermeable barrier. The inorganic platelets may be clay, such asmontmorillonite, vermiculite, mica, talc and combinations thereof.

Preferably, the inorganic oxide platelets are stable (i.e., do not burn,melt or decompose) at about 600 degrees C., more preferably at about 800degrees C. and most preferably at about 1000 degrees C. Vermiculite is apreferred platelet material for the refractory layer. Vermiculite is ahydrated magnesium aluminosilicate micaceous mineral found in nature asa multilayer crystal. Vermiculite typically comprises by (dry) weight,on a theoretical oxide basis, about 38-46% SiO₂, about 16-24% MgO, about11-16% Al₂O₃, about 8-13% Fe₂O₃ and the remainder generally oxides of K,Ca, Ti, Mn, Cr, Na, and Ba. “Exfoliated” vermiculite refers tovermiculite that has been treated, chemically or with heat, to expandand separate the layers of the crystal, yielding high aspect ratiovermiculite platelets. Suitable vermiculite materials are available fromSpecialty Vermiculite Products under the trade designations MicroLite963 and MicroLite 963HS

The thickness of an individual platelet typically ranges from about 5Angstroms to about 5,000 Angstroms more preferably from about 10Angstroms to about 4,200 Angstroms. The mean value of the maximum widthof a platelet typically ranges from about 10,000 Angstroms to about30,000 Angstroms. The aspect ratio of an individual platelet typicallyranges from 100 to 20,000.

Preferably, the platelets have an average diameter of from 15 to 25micrometers. In some other embodiments, the platelets have an averagediameter of from 18 to 23 micrometers.

In a preferred embodiment, the refractory layer further comprisescations arising from contact, at a temperature of from 10 to 50 degreesC., with an aqueous cationic rich solution at a cation concentration offrom 0.25 to 2N. The contact with the cationic solution occurs prior toassembling the refractory layer into a composite laminate. This cationictreatment provides enhanced stability to the refractory layer onexposure to fluids.

In some embodiments of this invention, the inorganic platelet layer maybe reinforced by a lightweight open weave fabric scrim either laid ontoa single platelet layer or placed between two layers of platelets so asto provide additional mechanical strength to the layer. The scrim can bemade from natural, organic or inorganic fibers with glass, cotton, nylonor polyester being typical examples. A glass fiber scrim is particularlypreferred. The scrim may be a woven or knit structure and has a typicalareal weight not exceeding 40 grams per square meter.

Preferably the refractory layer is continuous. By continuous is meantthat the layer is capable of being wound onto a roll without breakingapart. In some embodiments, the refractory layer is perforated toenhance bonding to an adhesive layer during subsequent processing. Theextent of perforation is determined by experimentation. Preferably, inorder to prevent compromising flame barrier properties, an individualperforation should not exceed 2 millimeters in maximum dimension. In apreferable embodiment, individual perforations should be spaced at least10 millimeters apart. The shape of the perforations is not critical,Suitable perforations include circles, squares, rectangles, ovals andchevrons.

The bond strength between the refractory layer and the surface of thepaper is at least 43 N/m (0.25 lb/in), preferably at least 14 N/m (0.8lb/in), If the bond strength is less than 43 N/m (0.25 lb/in), theinorganic refractory layer can peel off the substrate with a risk ofbreaks in the refractory layer. A bond strength of at least 140 N/m (0.8lb/in) ensures that the inorganic refractory layer does not separatefrom the substrate either during subsequent process steps or, once putin service, during the life span of the intended application. Bondstrength is sometimes referred to as Release Value. In this instance, itis the Release Value between the surface of the paper and theintumescent coating applied to the paper.

Third Component

The third component 23 has an areal density of from 88 to 678 gsm (2.6to 20 oz. per sq. yd.) and comprises a second fabric 28 of filamentaryyarns having a tenacity of at least 11 grams per dtex (10 grams perdenier) and a second polymeric layer 29, the second fabric of the thirdcomponent being adjacent to the refractory layer of the secondcomponent. The second polymeric layer is the innermost layer of thecomposite sheet. The second polymeric layer provides enhancedabrasion/scuff and puncture resistance, improved impact toughness aswell as an enhanced resistance to both physical mistreatment, chemicalcontact attack and permeation by liquids.

Preferably, the second polymeric layer maintains its toughness andflexibility over a wide temperature range, even at temperatures as lowas (−50° C. (−60° F.)), over the life span of the end product.

In some embodiments, the second fabric layer may be bonded to the secondpolymeric layer by means such as an adhesive, thermal bonding or byfasteners.

When an adhesive is used the adhesive layer may be a thermoplastic orthermoset resin. Thermoset resins include epoxy, epoxy novolac,phenolic, polyurethane, and polyimide. Thermoplastic resins includepolyester, polyetherketone, polyetheretherketone, polyetherketoneketone,polyethersulfone, and polyolefin. Thermoplastic resins are preferred.The adhesive may optionally contain up to 40 weight percent of a flameretardant ingredient. Suitable flame retardant ingredients includeantimony trioxide, halogenated flame retardants includingtetrabromobisphenol A, polybrominated biphenyls, Penta-, Octa-,Decabrominated diphenyl ether (oxide) and hexabromocyclododecane.Phosphorus containing flame retardants are also widely used.

The adhesive must be capable of activation at a temperature in the rangeof 75 to 200 degrees C. In some embodiments, the activation range isfrom 120 to 140 degrees C. By activation we mean that for a thermosetresin, the resin must bond to the polymeric layer and the fabric withinthe specified temperature range. For a thermoplastic resin, activationmeans that the resin softens and flows sufficiently to bond to thepolymeric layer and the fabric. The adhesive bond between the secondpolymeric layer and the second fabric is at least 263 N/m (1.5 lb/in).In some embodiments, the adhesive bond between the second polymericlayer and the second fabric is at least 315 N/m (1.8 lb/in), or even 876N/m (5 lb/in).

In some embodiments, the bond strength between the second fabric 28 andthe second polymeric layer 29 is at least 263 N/m (1.5 lb/in). Inanother embodiments, the bond strength between the second fabric and thesecond polymeric layer is at least 315 N/m (1.8 lb/in).

In some embodiments the second fabric may be optionally treated on oneor both sides with an inorganic coating such as a ceramic.

First and Second Fabrics

In some embodiments the first or second fabrics have an areal weight offrom 70 to 508 gsm (2.1 to 15 oz. per sq. yd.). In some otherembodiments, the fabric areal weight is from 101 to 373 gsm (3 to 11 oz.per sq. yd.). In some embodiments, the first fabric has an areal weightof from 101 to 170 gsm (3 to 5 oz. per sq. yd.). In some embodiments,the second fabric has an areal weight of from 170 to 270 gsm (5 to 8 oz.per sq. yd.).

The first or second fabrics may be woven or non-woven. Typical wovenfabric styles are plain, basket, leno twill or satin weaves. In oneembodiment, the first fabric is a plain weave fabric comprising 555 dtex(500 denier) KM2+ p-aramid yarns in an amount of 11 ends per cm (28 endsper inch) in both warp and weft directions. In another embodiment, thesecond fabric is a plain weave fabric comprising 1111 dtex (1000 denier)KM2 p-aramid yarns in an amount of 9.4 ends per cm (24 ends per inch) inboth warp and weft directions.

Fine denier yarn of the fabric combined with a tough polymeric filmleads to a significant enhancement in puncture resistance, and thusoverall durability, of the non-rigid composite sheet.

Nonwoven fabrics include fabrics in which the filaments are arranged ina random orientation or fabrics comprising filaments that are aligned inonly one direction. This latter type of fabric is also known as anon-crimped or unidirectional fabric.

In some embodiments the first and/or second fabrics are scoured or heatcleaned after weaving. Such processes are well known in the textileindustry to remove contaminants such as oil from the weaving process.

Preferably, the filamentary yarns of the first and second fabricscomprise aromatic polyamide or aromatic copolyamide. Glass fiber andcarbon fiber, especially carbon fiber based on polyacrylonitrile, mayalso be used.

The fabrics 25 and 28 are made from multifilament yarns having aplurality of filaments. The yarns can be intertwined and/or twisted. Forpurposes herein, the term “filament” is defined as a relativelyflexible, macroscopically homogeneous body having a high ratio of lengthto width across its cross-sectional area perpendicular to its length.The filament cross section can be any shape, but is typically circularor bean shaped. Herein, the term “fiber” is used interchangeably withthe term “filament”, and the term “end” is used interchangeably with theterm “yarn”.

The filaments can be any length. Preferably the filaments arecontinuous. Multifilament yarn spun onto a bobbin in a package containsa plurality of continuous filaments. The multifilament yarn can be cutinto staple fibers and made into a spun staple yarn suitable for use inthe present invention. The staple fiber can have a length of about 1.5to about 5 inches (about 3.8 cm to about 12.7 cm). The staple fiber canbe straight (i.e., non crimped) or crimped to have a saw tooth shapedcrimp along its length, with a crimp (or repeating bend) frequency ofabout 3.5 to about 18 crimps per inch (about 1.4 to about 7.1 crimps percm).

In some embodiments, the yarns have a yarn tenacity of at least 11 gramsper dtex and a modulus of at least 100 grams per dtex. In someembodiments, the yarns have a linear density of from 333 to 2222 dtex(300 to 2000 denier) or from 555 to 1111 dtex (500 to 1000 denier). Insome embodiments, the yarns of the first or second fabrics have a lineardensity of 555 dtex or of 1111 dtex.

When the polymer is polyamide, aramid is preferred. The term “aramid”means a polyamide wherein at least 85% of the amide (—CONH—) linkagesare attached directly to two aromatic rings. Suitable aramid fibers aredescribed in Man-Made Fibres—Science and Technology, Volume 2, Sectiontitled Fibre-Forming Aromatic Polyamides, page 297, W. Black et al.,Interscience Publishers, 1968. Aramid fibers and their production are,also, disclosed in U.S. Pat. Nos. 3,767,756; 4,172,938; 3,869,429;3,869,430; 3,819,587; 3,673,143; 3,354,127; and 3,094,511.

The preferred aramid is a para-aramid. The preferred para-aramid ispoly(p-phenylene terephthalamide) which is called PPD-T. By PPD-T ismeant the homopolymer resulting from mole-for-mole polymerization ofp-phenylene diamine and terephthaloyl chloride and, also, copolymersresulting from incorporation of small amounts of other diamines with thep-phenylene diamine and of small amounts of other diacid chlorides withthe terephthaloyl chloride. As a general rule, other diamines and otherdiacid chlorides can be used in amounts up to as much as about 10 molepercent of the p-phenylene diamine or the terephthaloyl chloride, orperhaps slightly higher, provided only that the other diamines anddiacid chlorides have no reactive groups which interfere with thepolymerization reaction. PPD-T, also, means copolymers resulting fromincorporation of other aromatic diamines and other aromatic diacidchlorides such as, for example, 2,6-naphthaloyl chloride or chloro- ordichloroterephthaloyl chloride or 3,4′-diaminodiphenylether.

Additives can be used with the aramid and it has been found that up toas much as 10 percent or more, by weight, of other polymeric materialcan be blended with the aramid. Copolymers can be used having as much as10 percent or more of other diamine substituted for the diamine of thearamid or as much as 10 percent or more of other diacid chloridesubstituted for the diacid chloride or the aramid.

Another suitable fiber is one based on aromatic copolyamide prepared byreaction of terephthaloyl chloride (TPA) with a 50/50 mole ratio ofp-phenylene diamine (PPD) and 3,4′-diaminodiphenyl ether is (DPE). Yetanother suitable fiber is that formed by polycondensation reaction oftwo diamines, p-phenylene diamine and 5-amino-2-(p-aminophenyl)benzimidazole with terephthalic acid or anhydrides or acid chloridederivatives of these monomers.

Glass fibers include “E” glass and “S” Glass. E-Glass is a commerciallyavailable low alkali glass. One typical composition consists of 54weight % SiO₂, 14 weight % Al₂O₃, 22 weight % CaO/MgO, 10 weight % B₂O₃and less then 2 weight % Na₂O/K₂O, Some other materials may also bepresent at impurity levels S-Glass is a commercially availablemagnesia-alumina-silicate glass. This composition is stiffer, strongerand more expensive than E-glass and is commonly used in polymer matrixcomposites.

In some embodiments the carbon fiber is a standard or intermediatemodulus fiber such as those available under the tradename Torayca orHexTow from Toray Industries or Hexcel Corporation. Typically, suchfibers have 3,000 or 6,000 or 12,000 or 24,000 filaments per tow.

In some embodiments first and/or second fabrics may optionally betreated with a flame retardant ingredient to aid flame propagationproperties of the non-rigid Flame Resistant Composite. Suitable flameretardant ingredients include antimony trioxide, halogenated flameretardants including tetrabromobisphenol A, polybrominated biphenyls,pentabrominateddiphenylether(oxide), octabrominateddiphenylether(oxide),decabrominateddiphenylyether(oxide) and hexabromocyclododecane.Phosphorus containing flame retardants are also widely used.

First and Second Polymeric Layers

The polymer of the first or second or both polymeric layers may be athermoplastic or thermoset polymer. A thermoplastic polymer ispreferred.

In a preferred embodiment, the first and second polymeric layers are ina form of a self-supporting film.

Suitable polymers include polyurethane, polyethylene, polypropylene,polyethylenenaphthalate, polyacrylonitrile, fluoropolymer, polyimide,polyketone, polyimide (Kapton®), polysulfone, polyarlene sulfide, liquidcrystal polymer, polycarbonate, and ionomers such asethylenemethacrylicacid copolymer (E/MAA).

Exemplary fluoropolymers include polyvinylfluoride (Tedlar®),etyhylenechlorotrifluoroethylene copolymer (Halar®) andpolytetrafluoroethylene (Teflon®). Exemplary polyketones includepolyetheretherketone (PEEK) and polyetherketoneketone (PEKK).

In one embodiment, the first polymeric layer is polyurethane. In anotherembodiment, the second polymeric layer is an ionomeric resin such asethylenemethacrylicacid copolymer. In yet another embodiment, the firstpolymeric layer is non-transparent and impervious to UV rays. Bynon-transparent and impervious to UV rays we mean that the firstpolymeric layer blocks at least 95% of UV rays, more preferably at least98% and most preferably 100% of UV rays especially those rays at theupper end of the UV spectrum.

In some embodiments the first and/or second polymeric layers have anareal weight of 17 to 170 gsm (0.5 to 5 oz. per sq. yd.) or from 34 to136 gsm (1 to 4 oz. per sq. yd.) or even from 67 to 102 gsm (2 to 3 oz.per sq. yd.).

In some embodiments, at least one surface of the first and/or secondpolymeric layers may be metalized. Preferably in the composite sheet,the metalized surface is on the side of the polymeric layer adjacent tothe first or second fabrics.

Test Methods

Flame penetration was measured according to 14 CFR 25.855 Appendix FPart III—Test Method To Determine Flame Penetration Resistance of CargoCompartment Liner (ceiling position

Tensile properties of the composite sheet were determined by ASTMD3039/D3039M-08 Standard Test Method for Tensile Properties of PolymerMatrix Composite Materials.

The dry tensile strength of the substrate was measured according toTAPPI T494 om-06 Tensile Properties of Paper and Paperboard (UsingConstant Rate of Elongation Apparatus).

The thickness of the substrate was measured by TAPPI T411 om-10Thickness (Caliper) of Paper, Paperboard, and Combined Board.

The dimensional stability of the substrate was rated based on itsability to hold flat (i.e. no moisture related wrinkles or creases) forat least 2 minutes when exposed to one-sided wetting.

The dry areal weight of the refractory layer was measured according toISO 536 (1995) Determination of Grammage and TAPPI T 410 Grammage ofPaper and Paperboard (Weight per Unit Area).

The moisture content of the refractory layer was measured according toISO 287 (1985) Determination of Moisture Content—Oven Drying Method.

The composite sheets were subjected to a flame test that replicated thetemperature and air mass flux test conditions of test method FAA FAR25.856(b), App. F, Part VII. The somewhat lower heat flux wascompensated with a higher air mass flux to replicate a requiredthermo-mechanical stress level to be exerted on the flame barriercomposites during the burn-through test.

EXAMPLES Example 1

A non-rigid composite sheet was prepared.

First Component

The first component comprised a woven fabric (first fabric) thermallybonded to a non-transparent 0.075 mm (3 mil) blown polyurethane film(first polymeric layer). The fabric had an areal weight of 125 gsm (3.7oz./sq. yd.). The fabric was a plain weave having 28 ends per inch inboth warp and weft and was woven from 556 dtex (500 denier) p-aramidKevlar® KM2+ yarns, merge 1W034. The bond strength between firstpolymeric film and first fabric was tested to be at least 437 N/m (2.5lbs/in).

Second Component

The second component comprised a refractory layer of vermiculite on0.125 mm (5 mil) Nomex® grade 413 paper substrate. 30 gsm of vermiculitewas coated onto the paper and subsequently treated with a 0.25N cationicdispersion of sodium chloride.

The vermiculite used was an aqueous dispersion of Microlite® 963HSobtained from Specialty Vermiculite Corporation, Enoree, S.C.

Third Component

The third component comprised a woven fabric (second fabric) thermallybonded to a 0.075 mm (3 mil) ionomeric Surlyn® film (second polymericlayer). The fabric had an areal weight of 220 gsm (6.5 oz./sq. yd). Thefabric was a plain weave having 24 ends per inch (9.4 ends/cm) in bothwarp and weft and was woven from 1111 dtex (1000 denier) p-aramidKevlar® KM2 yarns, merge 1W041. The bond strength between firstpolymeric film and first fabric was tested to be at least 262 N/m (1.5lbs/in).

The first, second and third components were assembled together as shownin FIG. 2A. Component 2 was not bonded to either component 1 orcomponent 3. For ease of handling all three components were sewntogether along their edges with Kevlar® thread.

The fabricated composite sheet was subjected, in a ceiling position, tothe FAA flame penetration test 14 CFR 25.855. The flame was applied onthe Surlyn® film side of the composite. The sample showed a goodresistance to flame penetration, with the inorganic refractory layeracting as an effective barrier to 927° C., +/−38° C. (1700° F., +/−100°F.)—flame with no flame penetration of the specimen within 5 minutesafter application of the flame source. The peak temperature measured at4 inches above the upper surface of the horizontal test sample did notexceed 204° C. (400° F.).

The composite sheet was also tested to comply with smoke & emissionrequirements as per14 CFR 25.853(d), Appendix F, Part V for smokeemission and to BSS 7239, Revision A for toxic gas determination. Theresults were deemed to be acceptable.

The mechanical strength of the composite sheet was also tested to complywith durability standards set by National Aerospace Standard NAS 3610for materials used for air cargo Unit Load Devices. The axial tensilestrength of 101.6 mm (4 inch) wide strips of the composite sheet was1,700+/−50 lbs or 771+/−22 kg (425+/−12.5 lb/in or 74228+/−2189 N/m).

Comparative Example A

A composite sheet was fabricated comprising a 322 gsm (9.5 oz./sq. yd).woven fabric thermally bonded between the 0.075 mm (3 mil) polyurethane(first polymeric layer) and the 0.075 mm (3 mil) Surlyn® (secondpolymeric layer) films of Example 1. The bond strength between the PUfilm and fabric was at least 437 N/m (2.5 lbs/in). The fabric was aplain weave having 24 ends per inch (94 ends per cm) in both warp andweft and was woven from 1667 dtex (1500 denier) p-aramid Kevlar® 29yarns, merge 1F211. The axial tensile strength of a 101.6 mm (4 inch)wide strip of the single layer composite was no greater than 900 lbs or408 kg (225 lb/in or 39403 N/m).

Comparable Example A was tested as complying with flammabilityrequirements of TSO C90a Cargo Pallets, Nets and Containers (Unit LoadDevices) specification for vertical and horizontal flame propagation.However, it lacked any effective flame barrier properties as, whenexposed to flame, the sample failed flame penetration within 30 secondsafter application of the flame source.

Example 2

This example was prepared as per Example 1 except that a thermoplasticfilm protective layer 32 was thermally bonded to the open face of therefractory layer of the second component. This construction as is shownin FIG. 2B. The thermoplastic protective film was a 0.021 mm (0.85 mil)gray Tedlar® SP PVF film, grade GY85SL2, available from DuPont.

The composite sheet of Example 2 was subjected, in a ceiling position,to the FAA flame penetration test 14 CFR 25.855. The flame was appliedon the Surlyn® film side of the composite. The sample showed a goodresistance to flame penetration, with the inorganic refractory layeracting as an effective barrier to 927° C., +/−38° C. (1700° F., +/−100°F.)—flame with no flame penetration of the specimen within 5 minutesafter application of the flame source. The peak temperature measured at4 inches above the upper surface of the horizontal test sample did notexceed 204° C. (400° F.).

Example 3 First Component

The first component comprised a woven fabric (first fabric) thermallybonded to a non-transparent 0.075 mm (3 mil) blown polyurethane film(first polymeric layer). The fabric had an areal weight of 220 gsm (6.5oz./sq. yd). The fabric was a plain weave having 24 ends per inch (9.4ends per cm) in both warp and weft and was woven from 1111 dtex (1000denier) p-aramid Kevlar® KM2 yarns, merge 1W041. The bond strengthbetween first polymeric film and first fabric was tested to be at least437 N/m (2.5 lb/in).

Second Component

The second component comprised a refractory layer of vermiculite on0.125 mm (5 mil) Nomex® grade 413 paper substrate. 30 gsm of vermiculitewas coated onto the paper and subsequently treated with a 0.25N cationicdispersion of sodium chloride.

The vermiculite used was an aqueous dispersion of Microlite® 963HS

Third Component

The third component comprised) ionomeric Surlyn® film (second polymericlayer). The fabric had an areal weight of 125 gsm (3.7 oz./sq. yd.). Thefabric was a plain weave having 28 ends per inch (11 ends per cm) inboth warp and weft and was woven from 556 dtex (500 denier) p-aramidKevlar® KM2+ yarns, merge 1W034. The bond strength between firstpolymeric film and first fabric was tested to be at least 262 N/m (1.5lb/in).

The first, second and third components were assembled together as shownin FIG. 2A. Component 2 was not bonded to either component 1 orcomponent 3. For ease of handling all three components were sewntogether along their edges with Kevlar® thread.

A composite sheet of this example showed similar resistance to flamepenetration and had a similar axial tensile strength as the compositesheet of Example 1.

What is claimed is:
 1. A non-rigid composite sheet comprising in order(i) a first component having an areal density of from 88 to 678 gsmcomprising a first fabric of filamentary yarns having a tenacity of atleast 11 g/dtex and a first polymeric layer. (ii) a second componenthaving an areal density of from 30 to 237 gsm comprising a substrate andan inorganic refractory layer, and (iii) a third component having anareal density of from 88 to 678 gsm comprising a second fabric offilamentary yarns having a tenacity of at least 11 g/dtex and a secondpolymeric layer, the second fabric of the third component being adjacentto the refractory layer of the second component, wherein (a) the yarnsof the first and second fabrics comprise aromatic polyamide, aromaticcopolyamide, glass fiber or carbon fiber, (b) the polymer of the firstpolymeric layer of the first component and second polymeric layer of thethird component is polyurethane, polyethylene, polypropylene,polyethylenenaphthalate, polyacrylonitrile, fluoropolymer, polyimide,polyketone, polyimide, polysulfone, polyarlene sulfide, liquid crystalpolymer, polycarbonate or an ionomer, (c) the substrate of the secondcomponent is a nonwoven fibrous sheet comprising fibers wherein thefibers are glass, aramid, crystalline ceramic oxide, silicon nitride,silicon carbide, oxidized polyacrylonitrile, carbon, and combinationsthereof, and (d) the first polymeric layer blocks at least 95% of UVrays.
 2. The composite sheet of claim 1, wherein the composite has abreak strength of at least 350 N/cm.
 3. The composite sheet of claim 1,wherein the composite sheet can withstand a flame temperature of 927° C.for 5 minutes without burn-through penetration when tested according toFAA test method 14 CFR 25.855 Appendix F Part III.
 4. The compositesheet of claim 1, wherein the composite sheet can withstand a flametemperature of 927° C. for 5 min without burn-through penetration andthe temperature 101 mm away from the side of the sheet remote from theflame does not exceed 204° C. when tested according to FAA test method14 CFR 25.855 Appendix F Part III.
 5. The composite sheet of claim 1,wherein the first or second fabrics have an areal weight from 70 to 508gsm.
 6. The composite sheet of claim 1, wherein the first fabric has anareal weight from 101 to 170 gsm.
 7. The composite sheet of claim 1,wherein the second fabric has an areal weight from 170 to 270 gsm. 8.The composite sheet of claim 1, wherein the filamentary yarns of thefirst and/or second fabrics comprise have a linear density of from 333to 2222 dtex.
 9. The composite sheet of claim 1, wherein the refractorylayer comprises vermiculite.
 10. The composite sheet of claim 1 whereinthe refractory layer has a dry areal weight of from 15 to 50 gsm. 11.The composite sheet of claim 1 wherein the inorganic refractory layerhas a moisture content of no greater than 10%.
 12. The polymer of claim1 wherein the ionomer is ethylenemethacrylicacid copolymer.
 13. A cargocontainer comprising a frame assembly, a plurality of side walls, aceiling and a floor wherein the sidewalls and ceiling comprise thenon-rigid composite sheet of claim 1.